Moodle image gallery fixer:
Turns the overview page with thumbnails into images so that
you don't have to deal with ugly lightbox gallery stuff.
WARNING: If you run this on a malicious gallery page, that might lead to XSS.javascript:[].concat.apply([], document.getElementsByClassName('lightbox-gallery-image-thumbnail')).forEach(function(e){e.setAttribute('style', ''); e.innerHTML = '<img src="'+e.href+'">'});[].concat.apply([], document.getElementsByClassName('lightbox-gallery-image-container')).forEach(function(e){e.setAttribute('style', '')});[].concat.apply([], document.getElementsByClassName('lightbox-gallery-image-frame')).forEach(function(e){e.className=''})

HTML5 player speed changer:
Lets you change the video playback speed on Youtube (and probably also other sites) arbitrarily. Also works with the HTML5 player of Netflix!
javascript:[].slice.call(document.getElementsByTagName('video')).forEach(function(e){e.playbackRate = prompt('new speed in percent?')/100})

HTML5 player speed changer box:
Adds a box in the bottom-right corner that lets you change the playback speed of all videos on the page. Press enter or defocus to apply speed change.
javascript:(function(e){e=document.createElement('input');e.size=4;e.style.position='absolute';e.style.bottom=e.style.right='0px';document.getElementsByTagName('body')[0].appendChild(e);e.onblur=function(){[].slice.call(document.getElementsByTagName('video')).forEach(function(v){v.playbackRate = e.value/100})};e.onkeydown=function(ev){if(ev.keyCode==13)return e.onblur(),false}})()